1. Field of the Invention
The present invention generally relates to an apparatus mounted on an automobile or motor vehicle for a dedicated short-range communication (hereinafter this apparatus will be referred to as the on-vehicle DSRC apparatus for short), which apparatus is employed in a dedicated short-range communication or DSRC system as one of the intelligent transport systems (also referred to as the ITS for short). More particularly, the present invention is concerned with the on-vehicle DSRC apparatus (hereinafter also referred to simply as the on-vehicle apparatus) which can enjoy not only the prolonged or extended life of a battery employed for supplying electric power to the on-vehicle apparatus for operation thereof by controlling or restraining the power consumption of the on-vehicle apparatus but also ensure an improved mounting facility for the on-vehicle DSRC apparatus.
2. Description of Related Art
In general, the on-vehicle DSRC apparatus is designed for the short-range communication only within a limited area or range of a road by making use of radio wave of a microwave band. More specifically, the radio communication is conducted between an on-road radio equipment installed at an appropriate location of a road and the on-vehicle DSRC apparatus for transferring data in the form of radio signals to thereby carry out various services such as the toll collection service, road information presentation service and the like, providing thus profitable conveniences for the drivers of motor vehicles, the managers who are in charge of controlling the traffic, parking area(s) and others.
As the systems in which the dedicated short-range communication or DSRC is adopted, there may firstly be mentioned the electronic toll collection system or ETC system for short. In addition, there are conceived the systems for toll collection at gas stations and drive-throughs, traffic information presentation services, etc., and for other various applications.
Among others, in the system or application for discounting the toll imposed on the motor vehicles having through a specified lane or lanes, as typified by the Environmental Road Pricing System as well as in other applications, there are conceived such types of discounts as “discount during special limited period”, “discount for customers” or the like. In short, the DSRC transaction system will be utilized not only for the accounting or toll collection but also for the toll discount and other various transactions in the not-so-distant future.
In the conventional on-vehicle DSRC apparatus known heretofore, the power supply (current feeding) to a radio unit and a data processing unit both incorporated in the on-vehicle DSRC apparatus is effected from an on-vehicle battery (i.e., battery mounted on the motor vehicle) and thus the circuits of both the radio unit and the data processing unit of the on-vehicle DSRC apparatus or some of these circuits are driven continuously, respectively, i.e., electrically energized continuously. For more particulars, reference may have to be made to, for example, Japanese Patent No. 2994362.
In this conjunction, it is noted that the radio unit and the data processing unit are generally implemented in a low-noise circuit structure with a view to preventing occurrence of bit errors in the received data. For this reason, the current or power consumption of the radio unit and the data processing unit is relatively large (ordinarily on the order of 100 mA in the continuous operation mode).
By the way, in recent years, the need for battery-driven type on-vehicle DSRC apparatus is increasing for making it possible to use the on-vehicle apparatus for the motor bicycles and/or with a view to improving the mounting facility or mountability of the on-vehicle DSRC apparatus.
However, in the conventional on-vehicle DSRC apparatus, the power consumption in the radio unit and the data processing unit is large (on the order of 100 mA), as mentioned above. This means that the time for continuous use of the on-vehicle DSRC apparatus is too short (about 5 hours) to be used in the practical applications, even if the battery of the capacity of about 500 mAH for e.g. portable phones is employed.
Furthermore, even in the case where the motor vehicle equipped with the DSRC apparatus is parking, rendering it unnecessary to use the ETC, the on-vehicle DSRC apparatus is continuously supplied with electric power, which means that the electric energy or power stored in the battery is wastefully used.
As is apparent from the above, the conventional on-vehicle DSRC apparatus suffers a problem that the practical utility is very poor because the power consumption of the radio unit and the data processing unit is ordinarily large and because the battery is wastefully used even in the situations where there is no need for effectuating the ETC operation.
Further, even in the case where the capacity of the battery incorporated in the on-vehicle DSRC apparatus becomes lower, it is impossible to recognize or detect the timing for exchanging the battery with a fresh one until the on-vehicle DSRC apparatus can not operate at all. Needless to say, when the battery capacity has been consumed, the on-vehicle DSRC apparatus can no more be used, unless the battery is exchanged, giving rise to another problem.
Moreover, since the on-vehicle DSRC apparatus is obligated not to be easily dismounted for the burglarproof purpose, it is necessary to transport a battery charger to a location of the on-vehicle DSRC apparatus mounted on the motor vehicle on the condition that the battery which can be electrically charged is employed as the built-in battery for the on-vehicle DSRC apparatus.